GPS Receiver Research Articles

Spectral Characteristics of Phase Fluctuations at High Latitude

AbstractIt has long been established that ionospheric electron density irregularities cause random rapid amplitude and phase fluctuations in trans‐ionospheric radio signals. Various types of ground‐based measurements, including radar and Global Navigation Satellite System (GNSS) receivers, have been utilized to gain insights into the plasma mechanisms that could lead to the development of these ionospheric irregularities. The spectral characteristics of radio wave signals emitted by GNSSs and detected by the Canadian High Arctic Ionospheric Network Global Positioning System (GPS) receivers are analyzed to try and identify the spectral signatures of the ionospheric plasma irregularities. In the polar region, we have confirmed that phase fluctuations in the GPS signal are not always accompanied by amplitude fluctuations. For the first time, a systematic comparison is conducted on the spectral properties of phase‐fluctuation events in the absence and presence of amplitude scintillations, respectively. More specifically, a spectral characterization is performed on 41 events recorded by three receivers positioned within the auroral oval. When fluctuations above the background level are solely observed in the signal's phase, the spectrum of phase variations exhibits a consistent steepness. Conversely, the presence of amplitude scintillation is accompanied by an increase in power at higher frequencies, resulting in shallower spectra. This analysis provides yet another physical element suggesting that the rapid fluctuations observed in the signal's amplitude may be caused by Fresnel‐scale irregularities arising from a gradient‐drift‐like instability while the phase variations seem to be consistent with a refractive mechanism caused by large‐scale ionospheric structures.

Investigation of the aberrant record from bus GPS receiver onboard FORMOSAT-7/COSMIC-2 satellite constellation in low Earth orbit

The FORMOSAT-7/COSMIC-2 (F7/C2) satellite constellation, a joint Taiwan-US collaboration mission, was launched on 25 June 2019. Following the FORMOSAT-3/COSMIC, the F7/C2 mission aims to provide global users the next-generation global navigation satellite system (GNSS) radio occultation data. The mission consists of six identical small satellites with an inclination angle of 24°, launched to the parking orbit of 720 km, and then transferred to the mission orbit of 550 km. Each satellite bus is equipped with two commercial off-the-shelf global positioning system receivers manufactured by Surrey Satellite Technology Ltd. for positioning, navigation, and timing functions. This receiver generates “GPS Receiver (bus GPSR) Warm Start Requested (WSR)” messages after commissioning, which could be considered as a kind of single event effect (SEE). More than 7000 WSR events have been recorded in 3 years after launch, providing another opportunity to investigate the SEE with the commercial off-the-shelf bus GPSR. In addition, the F7/C2 mission is the first satellite constellation that allows scientists to investigate the SEE using the same constellation at different altitudes of Low-Earth orbit. This study investigates and discusses the cumulative rate, distribution of WSRs, and their relationships between altitude and geomagnetic field. The statistical method is applied to define a warning area of the high probability occurring the SEE of this kind of component based on the geomagnetic field, whose corresponding strength is around 21,200/20,550 nT and close to the South Atlantic Anomaly area. Moreover, the relationships with space weather, including the disturbance of the Earth's magnetic field (Kp index) and the solar activity (F10.7 index), are also analyzed and reported.

THE BOTTOM RELIEF OF VYZYRKA POND (ODESSA REGION, ODESSA DISTRICT)

Problem Statement and Purpose. For arid conditions of southern Ukraine, the problem of preservation and use of the local water resources has been relevant for a long time. One of the types of adaptation of economic activity to the natural conditions of the area is artificial water bodies’ creation. Operation of ponds without repair work led to reduction of the water surface area of most of them, siltation, reduction of depths, overgrowth, as a result of which the ponds from water accumulators turned into evaporators. The publications review devoted to ponds and artificial reservoirs showed that their hydrochemical, hydrobiological regime, hydrological elements and ecological condition are mainly studying. The purpose of the research is to establish the regularities of the relief structure of the bottom of the pond in the village of Vyzyrka. Data & Methods. Field research was conducted in July 2021–2022. From two reservoirs, located within the village of Vyzyrka, the larger one was investigated. Work in the water area was carried out from the rowing boat Kolibri. The depths were determined with a Garmin Echo 200 echo sounder a geodetic rail. The use of the echo sounder made it possible to visually trace the relief of the bottom changes on the tacks and choose typical underwater points during relief measurements (ND31– 7.002.-2005). The depths were determined at 60 points, located evenly across the water area. The coordinates of measurement points were determined using a Garmin GPS72H GPS receiver. The journal of points was exported to Garmin Base Camp software. Results. Vyzyrska Pond has existed as an artificial reservoir since 1923. The relief has a trough-like shape inherited from the beam relief. Three areas are distinguished in the structure of the bottom relief: flat bottom of the northern part; underwater continuation of concave coastal slopes; the central depression stretches along the axis of the reservoir from southeast to northwest. The creation and use of artificial reservoirs leads to the development of geomorphological processes associated with the interaction of the native relief, which was formed in other physical and geographical conditions, with the water environment. Further studies of the pond are aimed at establishing the spatial distribution of hydrological elements in the water area of the pond in order to establish patterns of their change, which are important for the aquatic biota development.

Integration of Emergency Locator Transmitter (Elt) Of Aircraft With the Global Positioning System (Gps) Receiver - A Vlsi Design Approach

This paper deals with the VLSI design aspects of Integrated Emergency Locater Transmitter (ELT), an emergency equipment installed in the aircraft, with Global Positioning System (GPS) receiver. The Emergency Locator Transmitter (ELT) transmits distress signals at 406 MHz and this can be detected by the satellite system. But, these satellites cannot determine the location of the transmitting ELT. If the position information calculated by Global Positioning System (GPS) is encoded in the 406 MHz signals, the satellite system can decode the location of the crash immediately and the time required for the rescue operation is minimized. Also, this integrated equipment can be incorporated with additional features that help for non emergency operations. The aspects discussed in this paper include, principles of the ELT, satellite system concepts, specifications and regulations applicable, VLSI design concepts, compatibility with other aircraft systems, and advantages of the integrated ELTGPS system over the existing ELT system etc.

The Ionospheric Three-Dimensional Electron Density Variations Induced by the 21 August 2017 Total Solar Eclipse by Using Global Ionospheric Specification

Global Ionospheric Specification (GIS) is based on the Gauss–Markov Kalman filter to assimilate the slant total electron content (TEC) observed from ground-based GPS receivers and space-based radio occultation instrumentations in order to reconstruct three-dimensional (3D) ionospheric electron density structure, and it can remotely sense and monitor the weather condition in space. In this study, five minutes of high temporal resolution GIS is implemented in order to reconstruct the 3D electron density structure on the 21 August 2017 total solar eclipse and analyze the variations induced by the moon’s shadow. To obtain more information of the ionosphere, from the extend 2200 GPS stations on the continental United States, are added for assimilation. The results show the ionosphere peak height (hmF2) uplift was 30–50 km altitude in latitude 25–40°N, and that the electron density depletion at higher altitudes (400 km) has a more noticeable time delay than at low altitudes (200 km), especially in low-latitude regions.

Geospatial Approach to Route Optimisation for Security Architecture Improvement

Understanding the complexity of road networks is tiring, especially in finding the optimum routes for emergency response. Dynamic route optimisation is a decision-making process powered by mathematical models to formulate a strong basis for predicting the best path between any two points in a road network. Exploring the numerous interconnected routes in and out of a road network provides a strong foothold for securing lives and properties. This study presents the findings of route optimisation at the Federal University of Technology Minna, Gidan Kwano Campus. High Target Differential Global Positioning System receiver (DGPS), Handheld GPS (Garmin GPSmap 60Cx), Quick Bird Satellite Imagery, and Google Earth Images were used for data acquisition purposes. An ArcGIS network analyst for optimum route identification based on Dijktra’s algorithm was utilised for analysis. Five different optimisation tests were done and the optimised routes were compared with alternative routes from the network. The total travel distances for alternative and optimum routes are 11852.414 m and 16614.156 m respectively while the total travel times for alternative and optimum routes are 2135.35 s and 2993.25 s respectively. The study revealed all optimum routes are faster cumulatively by (11.7%) and are best for security and emergency responses. Ten unauthorised access roads to the campus were identified. The number of routes paving access to the campus shows that efforts towards ensuring security must be increased.

A Novel Traffic Characteristics Aware and Context Prediction Protocol for Intelligent Connected Vehicles

Digital maps have been installed and attached to vehicles recently. They help with the GPS receivers to determine the relative locations of vehicles to other existing traffic and objects over the road network such as entrance/exit points, obstacles, road intersections, etc. This helps drivers or autonomous vehicles to decide the most appropriate reaction, in terms of speed, take-over, or stop operations ahead of time. Several daily traveling vehicles do not have digital maps. Besides, digital maps are vulnerable to being destroyed or inaccurate. They require regular updates due to the continuous construction and re-design of the road networks. These constructions aimed to enhance the road design and the traffic efficiency there. Moreover, accidents, broken vehicles, traffic congestion, or other ad-hoc obstacles appear unpredictably over the road network. In this paper, we aim to introduce a prediction protocol that gathers and analyzes the traffic characteristics of vehicles over the investigated road scenario using wireless transceivers in vehicles. Then, it predicts the physical and traffic context based on the analyzed traffic data. This protocol can replace the absent or broken digital maps in vehicles. It also can be used to verify the correctness of the digital map in vehicles. From the experimental results, we can infer that the proposed protocol has succeeded in predicting the road context over highways and downtown scenarios. More accurate and better predictions are acquired by increasing the percentage of wireless transceiver-equipped vehicles.

Joint Detection and State Estimate with GSAs in PMU-Based Smart Grids

The Phasor Measurement Unit (PMU) with a GPS signal receiver is a synchronized sensor widely used for power system state estimation. While the GPS receiver ensures time accuracy, it is vulnerable to network attacks. GPS spoofing attacks can alter the phase angle of PMU measurement signals and manipulate system states. This paper derives a power system state model based on PMUs under GPS spoofing attacks, according to the characteristics of changes in bus voltages and branch currents after GSA. Based on the characteristics of this model, a detection and correction algorithm for attacked data is proposed to detect GSA and correct attacked measurements. The corrected measurements can be used for power system state estimation. Simulation results on the IEEE 14-bus system show that the proposed algorithm improves the accuracy of state estimation under one or multiple GSAs, especially when multiple GSAs are present, compared to classical Weighted Least Squares Estimation (WLSE) and Alternating Minimization (AM) algorithms. Further research indicates that this algorithm is also applicable to large-scale networks.

Adaptive Multi-Robot Communication System and Collision Avoidance Algorithm for Precision Agriculture

In precision farming technology, the interest of the researchers has been focused on the applications of autonomous mobile robots for agricultural operations such as planting, inspection, spraying, and harvesting. However, each autonomous robot generally performs a single agricultural task. In this context, complete autonomy in precision farming can be achieved by using coordinated multi-robot systems that can easily and safely cooperate to accomplish agricultural tasks. The efficiency of the multi-robot system depends on the number of robots, the size of the robots, the distance between each robot, the instant location and heading angle of the robots, and the size of the farmland. This paper describes the development of wireless Robot to Robot (R2R) communication system architecture and the collision avoidance algorithm for multi-robot precision farming applications. The developed system uses the fusion of a digital compass and GPS receiver for wirelessly broadcasting the spatial and temporal data of the mobile robots through WiFi. In this study, WiFi broadcasting was chosen for reasons such as the advantages of long wireless signal range and strength, not being easily affected by weather and dust, low cost, and so on. The proposed system realizes the real-time wireless broadcasting of the mobile robot information for eliminating the collision of mobile robots and improving the level of safety management. The results show that the system has flexible, reliable, and adaptable solution, and thus can increase the efficiency of the multi-robot system in precision farming applications.

Seasonal Variation in the Activity Budget and Daily Path Length of Semi-Provisioned Rhesus Macaques (Macaca mulatta) in Daunne Forest, Nawalpur, Nepal

Rhesus macaques (Macaca mulatta, Mammalia: Primates: Haplorhini: Cercopithecidae) show a great deal of adaptability in different types of habitats. Understanding how these animals allocate their time with regard to their daily activities and ranging behavior is helpful to the design of effective conservation plans by allowing us to better understand their ecological necessities and behavioral responses to environmental changes. This study examined seasonal variation in the activity budget and ranging behavior of a semi-provisioned group of rhesus macaques inhabiting the Daunne Devi Temple area in the Daunne Forest, a subtropical forest in mid-hill of central Nepal. Behavioral data were collected on the adult members of the group using focal animal sampling from 27 October 2021 to 10 May 2022 (for a total of 29 days /227 hours of observation) during three time periods of the day: morning, 7.00–11.00 am; afternoon, 11.00–2.00 pm; and late afternoon, 2.00–6.00 pm. Simultaneously, ranging behavior was recorded by instantaneous scan sampling at 10-minute intervals with the aid of a GPS receiver. The adults in the study group spent the majority of the time resting (33.83%), followed by moving (26.67%), feeding (22.92%), and grooming (15.42%). Males spent significantly more time resting and moving, whereas females spent significantly more time in feeding and grooming. The time invested by the rhesus macaques in different activities showed seasonal variation, but lacked statistical significance. Daily path length ranged between 540.1–2905.4 m (mean = 1590 ± 576.96 m) with a statistically significant seasonal difference that might be attributed to the number of temple visitors and availability of provisioned food. Although the sample size was small and study duration was short, this is one of only a few studies providing empirical evidence suggesting the seasonal variation in activity budget and daily path length of semi-provisioned rhesus macaques.

Micro urban spaces and mental well-being: Measuring the exposure to urban landscapes along daily mobility paths and their effects on momentary depressive symptomatology among older population

The urban environment plays an important role for the mental health of residents. Researchers mainly focus on residential neighbourhoods as exposure context, leaving aside the effects of non-residential environments. In order to consider the daily experience of urban spaces, a people-based approach focused on mobility paths is needed. Applying this approach, (1) this study investigated whether individuals’ momentary mental well-being is related to the exposure to micro-urban spaces along the daily mobility paths within the two previous hours; (2) it explored whether these associations differ when environmental exposures are defined considering all location points or only outdoor location points; and (3) it examined the associations between the types of activity and mobility and momentary depressive symptomatology. Using a geographically-explicit ecological momentary assessment approach (GEMA), momentary depressive symptomatology of 216 older adults living in the Ile-de-France region was assessed using smartphone surveys, while participants were tracked with a GPS receiver and an accelerometer for seven days. Exposure to multiple elements of the streetscape was computed within a street network buffer of 25 m of each GPS point over the two hours prior to the questionnaire. Mobility and activity type were documented from a GPS-based mobility survey. We estimated Bayesian generalized mixed effect models with random effects at the individual and day levels and took into account time autocorrelation. We also estimated fixed effects. A better momentary mental wellbeing was observed when residents performed leisure activities or were involved in active mobility and when they were exposed to walkable areas (pedestrian dedicated paths, open spaces, parks and green areas), water elements, and commerce, leisure and cultural attractors over the previous two hours. These relationships were stronger when exposures were defined based only on outdoor location points rather than all location points, and when we considered within-individual differences compared to between-individual differences.

BSafe-360: An All-in-One Naturalistic Cycling Data Collection Tool.

The popularity of bicycles as a mode of transportation has been steadily increasing. However, concerns about cyclist safety persist due to a need for comprehensive data. This data scarcity hinders accurate assessment of bicycle safety and identification of factors that contribute to the occurrence and severity of bicycle collisions in urban environments. This paper presents the development of the BSafe-360, a novel multi-sensor device designed as a data acquisition system (DAS) for collecting naturalistic cycling data, which provides a high granularity of cyclist behavior and interactions with other road users. For the hardware component, the BSafe-360 utilizes a Raspberry Pi microcomputer, a Global Positioning System (GPS) antenna and receiver, two ultrasonic sensors, an inertial measurement unit (IMU), and a real-time clock (RTC), which are all housed within a customized bicycle phone case. To handle the software aspect, BSafe-360 has two Python scripts that manage data processing and storage in both local and online databases. To demonstrate the capabilities of the device, we conducted a proof of concept experiment, collecting data for seven hours. In addition to utilizing the BSafe-360, we included data from CCTV and weather information in the data analysis step for verifying the occurrence of critical events, ensuring comprehensive coverage of all relevant information. The combination of sensors within a single device enables the collection of crucial data for bicycle safety studies, including bicycle trajectory, lateral passing distance (LPD), and cyclist behavior. Our findings show that the BSafe-360 is a promising tool for collecting naturalistic cycling data, facilitating a deeper understanding of bicycle safety and improving it. By effectively improving bicycle safety, numerous benefits can be realized, including the potential to reduce bicycle injuries and fatalities to zero in the near future.

Street direction classification using implicit vehicle crowdsensing and deep learning

GPS navigation systems are nowadays used extensively by drivers to reach locations and minimize traveling time. It is crucial to have up-to-date map information for their correct functioning. Map updating approaches leveraging human intervention may lag behind frequent changes in urban road arrangements like allowed directions. In this work, we use a combination of crowdsensing and deep learning techniques to extract information about allowed directions of the streets in a completely automated way. We present a faster and more sustainable alternative to currently adopted methods to keep maps’ details updated, based on crowdsensing without user intervention. In particular, we use data from on-vehicle GPS receivers, onboard cameras, and OSM queries. We describe experiments with data from different sources, such as real datasets and trip simulators. To address the problem of classifying street allowed directions, we propose two approaches: the first is based on an MLP on GPS traces, and the second consists in adopting a ResNet50 model on onboard camera imagery. We discuss how the cheaper and more easily deployable first approach delivers performance comparable to the second.

The methods of modeling the terrain of fields for precision farming technologies

According to aerial photography and two models of GPS receivers, the digital models of the slope were built using the "ArcGIS" tools. The comparison of the quality of digital terrain models created with use of three sources was carried out in this paper. The data obtained from GPS receivers have a significant altitude error; however, taking this factor into account, new equipment determines the location of a point in space more accurately, minimizing sharp altitude indicators. The quality of terrain models depends on the model of GPS receiver and the number of points, but anyway aerial photography is the best source for creating digital terrain models. Although it has a high accuracy of output data, it is worth considering that this method is very expensive. The resulting models can be used to design elements of precision farming technology.

Flight Demonstration of High Altitude Aircraft Navigation With Cellular Signals

This article presents the first demonstration of navigation with cellular signals of opportunity (SOPs) on a high-altitude aircraft. An extensive flight campaign was conducted by the Autonomous Systems Perception, Intelligence, and Navigation Laboratory in collaboration with the U.S. Air Force to sample ambient downlink cellular SOPs in different regions in Southern California, USA. Carrier phase measurements were produced from these signals, which were subsequently fused in an extended Kalman filter along with altimeter measurements to estimate the aircraft’s state (position, velocity, and time). Three flights are performed in three different regions: 1) rural, 2) semiurban, and 3) urban. A multitude of flight trajectories and altitudes above ground level (AGL) was exercised in the three flights: 1) a 51-km trajectory of grid maneuvers with banking and straight segments at about 5,000 ft AGL, 2) a 57-km trajectory of a teardrop descent from 7,000 ft AGL down to touchdown at the runway, and 3) a 55-km trajectory of a holding pattern at about 15,000 ft AGL. The estimated aircraft trajectory is computed for each flight and compared with the trajectory from the aircraft’s onboard navigation system, which utilized a GPS receiver coupled with an inertial navigation system and an altimeter. The cellular SOPs produced remarkable sustained navigation accuracy over the entire flight trajectories in all three flights, achieving a 3D position root mean-squared error of 10.53 m, 4.96 m, and 15.44 m, respectively.

Optimum Model for Tracking of Moving Objects

In wireless communication, it is a challenge to find the accurate position of moving objects. The presented work proposes the GPS receiver to measure the position and velocity of moving objects. These measurements are dynamic, the Least Squares (LS) technique is used to linearize the measurement for further processing. Afterward, the time difference of arrival (TDOA) mythology is applied. The obtained data is then processed through a Kalman filter to mitigate non-line-of-sight errors and smoothen the range values. The Kalman filter applies standard deviation on received data and performs an NLOS/LOS hypothesis test. By processing the received data, the algorithm generates readings that mitigate the NLOS error and reduces position error. The simulations demonstrate that the proposed algorithm reduced the noise by 28.64% and 34.4% in LOS and NLOS regions respectively. These findings indicate that the accuracy of object tracking was significantly improved as compared to other algorithms while also being less computationally intensive and cost efficient.

Analysis of navigation system accuracy characteristics for micro UAVs

The article analyzes the noise influence of the main types that arise in the process of exchanging navigational information between the GPS receiver of an micro-class unmanned aerial vehicle and the global satellite navigation system using an improved advanced simulation model in the Matlab – Simulink software environment, which allows building a representative statistical model in the process designing algorithms of the navigation system of unmanned aerial vehicles. With the help of modeling the process of choosing the receiver gain factor of an unmanned aerial vehicle and the study of the influence of the quality of reception and processing navigation signals during the increase of the distance relative to the satellite signal of the global navigation satellite system, it was established that with an increase in the gain factor of the antenna, the noise level decreases. However, an increase in the amplification factor leads to an increase in the dimensions of the antenna, as well as, accordingly, an increase in energy consumption, which does not meet the requirements for the mass-dimensional indicators of the microclass of unmanned aerial vehicles. Also, the article investigated the operation process of microelectromechanical systems of platformless inertial navigation systems, namely, at the moment of the disappearance of global satellite systems at a time interval of up to 300 seconds, to determine the error of calculating the parameter of the vertical component (height) and vertical speed of an unmanned aerial vehicle. According to the simulation results, it was found that the orientation and navigation of unmanned aerial vehicles in autonomous flight depend significantly on random errors of microelectromechanical systems of platformless inertial navigation systems, these include random angle wandering (zero noise drift); the influence of linear acceleration of the accelerometer sensor, by studying the noise model of errors microelectromechanical systems to determine the eight velocity parameter in autonomous flight mode, which is of a significant nature.

A comparison of Jason-2 plasmasphere electron content measurements with ground-based measurements

Abstract. Previous studies utilizing the Global Positioning System (GPS) receivers aboard Jason satellites have performed measurements of plasmasphere electron content (PEC) by determining the total electron content (TEC) above these satellites, which are at altitudes of about 1340 km. This study uses similar methods to determine PEC for the Jason-2 receiver for 24 July 2011. These PEC values are compared to previous determinations of PEC from a chain of ground-based GPS receivers in Africa using the SCORPION method, with a nominal ionosphere–plasmasphere boundary at 1000 km. The Jason-2 PECs with elevations greater than 60∘ were converted to equivalent vertical PEC and compared to SCORPION vertical PEC determinations. In addition, slant (off-vertical) PECs from Jason-2 were compared to a small set of nearly co-aligned ground-based slant PECs. The latter comparison avoids any conversion of Jason-2 slant PEC to equivalent vertical PEC, and it can be considered a more representative comparison. The mean difference between the vertical PEC (ground-based minus Jason-2 measurements) values is 0.82 ± 0.28 TEC units (1 TEC unit=1016 electrons m−2). Similarly, the mean difference between slant PEC values is 0.168 ± 0.924 TEC units. The Jason-2 slant PEC comparison method may provide a reliable determination for the plasmasphere baseline value for the ground-based receivers, especially if the ground stations are confined to only midlatitude or low-latitude regions, which can be affected by a non-negligible PEC baseline.

Algorithms for improving the position determination of an UAV equipped with a single-frequency GPS receiver for low-altitude photogrammetry

Algorithms for improving the position determination of an UAV equipped with a single-frequency GPS receiver for low-altitude photogrammetry

Automatic Pothole and Humps Detection System of Roads

One of the largest difficulties in developing countries is road maintenance. The nation's economy benefits greatly from well-maintained roads. Finding pavement issues like potholes and humps not only assists in preventing crashes and vehicle damage but also helps with road upkeep. In order to identify potholes and speed humps on roads and inform drivers in a timely manner so they can avoid collisions or serious injuries, this report highlights the pothole detection methods that have been created. Potholes and humps are detected using ultrasonic sensors. The suggested system uses a GPS receiver to record the geographic coordinates of potholes and humps. This pothole detection system’s idea is to alert the drivers if the pothole is detected on the way to reduce the speed of the vehicle or choose another path.